Reliable deformation measurement is required for proper quantification of fire performance of concrete structures. Predictive capability of models for many critical properties, including Young's moduli, stress-strain relationships and load-induced thermal strains, is first and foremost dependent on such reliable deformation capturing. This paper first presents a state-of-the-art review of existing methods for capturing deformation of concrete structures at elevated temperatures. Key merits, limitations and challenges associated with each measuring technique are discussed. It is shown that existing testing facilities and measuring instruments generally do not allow reliable direct measurement of displacement and strain of high-temperature concrete. As a result, the deformation has typically been captured either indirectly or outside the heated zones, inevitably introducing additional uncertainties and errors that are difficult to be adequately quantified. On the basis of that review, the paper details a new test setup for reliable, non-contact fullfield deformation capturing of concrete structures at high temperatures using 3D Digital Image Correlation technique. Key features of the new setup that enable to successfully address major challenges of thermal boundary condition, thermal stability of speckle pattern, contrast of image and hot air movement are highlighted. Evidence giving confidence to the reliability of the new setup are then presented, together with likely applications of such setup and their potential positive impact on the ongoing transitioning towards performance-based structural fire engineering.

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